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Proto Palace Zone is a secret Zone added in the 2013 re-release of Sonic the Hedgehog 2. It is based on the original Hidden Palace Zone prior to its deletion for the original Sonic the Hedgehog 2 (as seen in the Nick Arcade and Simon Wai prototype versions).


As of version 3.0.9, to access Proto Palace Zone, the player must first access the Level Select (start the game in "No Save Mode", tap the S-E-G-A letters when the Sega logo appears and hold two fingers at the title screen), input the Debug Mode code in the Sound Test (01, 09, 09, 02, 01, 01, 02, 04) and then must input an exclusive code in the Sound Test as follows: 03, 03, 03, 0B, 10, 10, 10, 04. (A Ring sound will play if successful.) Then, the player must select Hidden Palace Zone.

While the layout still remains unchanged from the prototype versions, changes were still made, such as platforms being added over the mid-level pit and newly functioning water slides as seen in the official Hidden Palace Zone. The Redz badniks also have their original behaviour restored. The infamous Tails Monitor is also present which still functions as a regular 1-Up regardless of the character(s) who breaks it. If the player jumps on the "Master Emerald"-like object, they will be warped back to the Level Select. The background music used for Proto Palace Zone is the unused Track #10.


  • If the player dies in this Zone by any means, the game will not load this Zone and will load Hidden Palace Zone instead.
  • If the player "clears" this Zone (using Debug Mode to place a Signpost or Capsule), the player will be transported to Oil Ocean Zone.
  • As the player is sent back to level select screen when they touch the emerald it means that part of the zone cannot be accessed without Debug Mode.


Title card




Name Artist(s) Length Music Track
Sound Test 10 Masato Nakamura 0:58

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